New guide to who really shouldn't eat gluten

You've got abdominal pains, bloating, fatigue and foggy thinking. You feel worse after eating wheat or other foods with gluten, and better when you avoid them.

Is it a wheat allergy, celiac disease or the power of suggestion, given all the buzz around gluten-free diets? Or might it be an ailment medicine doesn't officially recognize yet?

Aiming to clarify the situation, a group of 15 experts from seven countries is proposing a new classification system for the gluten-related disorders plaguing a growing number of people around the world for unknown reasons.

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The proposal defines a spectrum of illnesses based on the kind of immune defenses people mount to gluten, from wheat allergies to autoimmune responses, such as celiac disease, in which the body mistakenly attacks its own tissue.

The experts also propose a third category for "gluten sensitivity," in which patients report the same symptoms as celiac disease but test negative for telltale antibodies. Some doctors have dismissed such complaints as imaginary, or fueled by the boom in gluten-free foods.

U.S. sales of gluten-free foods grew to $2.3 billion in 2010, more than doubling from 2006, according to Packaged Facts. The market-research firm surveyed 277 consumers of gluten-free products in 2010, and nearly half said they perceived them as "generally healthier."

"Confusion about gluten sensitivity has been rampant," said Alessio Fasano, director of the University of Maryland's Center for Celiac Research and a co-author of the proposal, published this week in the journal BMC Medicine. "That prompted a few of us to say, 'Let's put some facts on the table to assess what's known and what's not known.' "

The proposal—partly supported by a maker of gluten-free products, Italy's Dr. Schär AG—also spells out diagnostic criteria to help physicians determine which, if any, disorder a patient suffers from. "It is well possible that many individuals are on a gluten-free diet for no sound medical reasons," the authors noted.

The American Gastroenterological Association says that much more needs to be known about gluten sensitivity before official guidelines can be devised—including how many people suffer from it and to what degree.

About 1 percent of people in the U.S. have celiac disease, a fourfold increase over the past 50 years. Some gastroenterologists say that for every patient with celiac disease, they see six to eight who have the same symptoms, but without the tell-tale antibodies or intestinal damage needed to confirm celiac.

Evidence is mounting that gluten sensitivity does exist. Fasano and colleagues last year compared blood samples and intestinal biopsies from people with suspected gluten sensitivity to those with confirmed celiac disease and healthy controls, and found distinct differences in each.

And in a study published last year, researchers in Australia showed in a double-blind, placebo-controlled trial that subjects with suspected gluten sensitivity had substantially fewer symptoms on a gluten-free diet than control subjects who unknowingly ingested gluten.

"Many physicians would roll their eyes and say, 'God, another crazy person with food sensitivities,' " said Peter Green, director of the Celiac Disease Center at Columbia University and a co-author of the proposal. "It's only now that studies are coming out showing that there's something real about gluten sensitivity."

In fact, he noted that patients with gluten sensitivity often have even more severe symptoms than those with celiac disease, which is frequently "silent" or asymptomatic, even though antibodies to gluten are slowly damaging their intestinal tracts. That's partly why celiac disease is under-diagnosed, he said.

Confusing the picture further are private labs that offer tests of stool or saliva that they say can definitively diagnose gluten sensitivity. Experts say that such tests haven't been validated and shouldn't be relied on for a diagnosis. "If anyone claims they have a test that is specifically for gluten sensitivity, there is no such thing, though I'm not ruling it out in the future," said Fasano.

He and other researchers are hoping to find a biomarker that can officially diagnose gluten sensitivity. But for now, the proposal notes, it can only be diagnosed by ruling out the other disorders.

Specifically, it says that physicians should suspect gluten sensitivity when patients complain of abdominal pain, bloating, diarrhea, constipation, anemia and other celiac symptoms, but don't have wheat allergies or the antibodies seen with celiac disease. If a biopsy is done, it generally won't show damage to the intestinal villi.

Only about half of people with gluten sensitivity have one of the two gene variations seen in virtually all celiac patients, so gene tests can rule out celiac, but not diagnose gluten sensitivity conclusively. (The blood tests cost about $100; the gene test about $300, and the biopsy $600 or more.)

Ultimately, the best test for gluten sensitivity is to see whether symptoms improve on a gluten-free diet. To avoid the power of suggestion, some doctors give patients blind tests with foods that may or may not contain hidden gluten.

Experts urge people who suspect they have problems with gluten to be tested for celiac disease before going gluten-free on their own. Otherwise, with no gluten to react to, their blood tests will show false negatives.

"This is the single biggest problem I see, and I see it every day in practice," said Joseph Murray, a celiac expert at the Mayo Clinic in Rochester, Minn.

Convincing patients who feel better to go back on gluten for testing purposes may be a hard sell. But getting a firm diagnosis is crucial, experts say, because those with celiac disease need to be on a strict gluten-free diet for the rest of their lives, or risk long-term complications including osteoporosis, infertility and some cancers. Those with gluten sensitivity may be able to eat small quantities occasionally without problems.